In general, a sensor network includes a set of sensor nodes as its basic unit. Its application service is primarily to exchange and control necessary information through wireless communication among these sensor nodes, which has been recently extended a great deal to accident surveillance of several kinds, real-time information gathering as well as some application fields that require reliability.
For sensor network application services such as accident surveillance of several kinds, real-time information gathering, it needs to resolve issues like collision avoidance resulting from several factors in order to ensure real-time surveillance based on accidents or reliability and at the same time the sensor network should be able to survive for a sufficiently long period of time. In this regard, a low-power method for media access control is of great importance in order to improve the efficiency in energy consumption and maintenance cost for a network of sensor nodes that use a limited energy source based on batteries.
Nonetheless, the development of most conventional communication techniques has been focused on low-power communication techniques and the low-power communication techniques that have been proposed until now use a method that lowers the power consumption primarily by repeating a cycle of motion and sleep in order to minimize unnecessary movements.
On the other hand, it has been well known that because a radio-frequency transceiver, i.e., a communication module, consumes energy tens or hundreds of times more than a microcontroller unit in general, the energy consumption is mostly due to idle listening and overhearing, particularly in a sensor network environment, that is, when a transceiver spends energy as it continuously stands by for reception even in a situation without any transmission sensor node and when neighboring nodes that do not participate in transmission receive packets unnecessarily, respectively. Therefore, in order to attain low-power operation, a given cycle of wakeup, execution and sleep is employed and then the energy consumption of a node is reduced effectively by adopting a low duty cycle with an elongated period.